The specific aim of this proposal is to provide a quantitative X-ray microprobe facility for investigators in the Institute of Dental Research and the School of Dentistry. Because of our existing TEM/SEM core facility we have the capability of incorporating both energy dispersive (EDS) and wavelength dispersive (WDS) electron probe microanalyzers to our ISI 100B scanning electron microscope. The design of this system will be such as to allow quantitative analyses of both light and heavy elements, peak overlap, and spectrum resolution, which requires the use of both WDS and EDS systems. Additional equipment already present in the laboratory to be used in conjunction with the electron probe includes a LaB6 gun with ion pump, Robinson backscatter detector, and a transmitted electron detector (STEM) and specimen holder. This complete electron probe system will be used by a number of investigators who will be studying various aspects of dental research and cellular pathophysiology. The proposed system will be used to provide quantitative analsysis of the relationship of F and dental caries. Studies will be conducted to determine the process of demineralization and remineralization and the fluoride uptake by mineralized dental tissues, requiring the analyses of F in low concentrations greater than 100 ppm, Ca and P. Furthermore, acid etch studies will be done to evaluate the relationship between Ca and P. Evaluation of light elements as well as spectrum analysis will be conducted on a variety of dental restorative materials. Studies of decalcified and calcified dentin as well as protein crystals will require analysis of elements which are in low concentrations (1.0 to 0.1 wt.%). The system will also be used to examine sectioned tissue (in the STEM holder) for the presence of intrinsic elements and/or cytochemical reaction products which stain these elements. The former include Na, K, Ca, Mg, P, S and Fe within the cell. The cytochemical reaction products include Fe, Ag, Pb, Os, Sb, Au. The electron probe will allow simultaneous evaluation of several of these elements or multiple cytochemical reaction products within the same organelle. Tissues to be examined will include blood cells, connective tissue cells and matrix, epithelial cells and secretions.